Follow-up after PRP injection The study subjects followed the instructions given by the doctors during the experiment and the second PRP injection was administered four weeks after the first injection. The pain score and the functional score were measured two months, four months, and six months after the second injection using the Visual Analogue Scale (VAS), the Cincinnati knee rating system (CKRS), and the Lysholm knee scale (LKS). The clinical score was calculated after determining the times of evaluation as level 1 (before the injection), level 2 (the second injection), level 3 (two months after the second injection), level 4 (in four months after the second injection), and level 5 (in six months after the second injection).